Method of making pump gears



1938. B. A. LINDERMAN 2,126,200

METHOD OF MAKING PUMP GEARS Filed March 14, 1935 2 Sheets-Sheet 1 i 3 4Imeniorz E i wk l 4 Bart CLLLncM/r'marv @z- C6014? m00@@s Patented Aug.9, 1938 UNITED STATES PATENT OFFICE Claims.

This invention relates to a new article of manufacture and to the methodof producing it, and more particularly to a pump of the gear type and toa novel method of producing the severalpump 5 parts.

In accordance with the present invention the several parts of a pump ofthe gear type, including the operating gears, are produced by a diecasting operation. After the die casting certain machining operationsmay be performed upon the castings but the teeth of the gear elementsare formed by the die casting process, and the machining operationswhich may be required upon the gears do not include any tooth cutting orshaping. Milling and tooth cutting operations, which are a source ofconsiderable expense in the production of gears,'are therefore avoided.The invention contemplates die casting the parts of hard and strongwear-resisting metal, or die casting them of softer metal and thereaftercoating them with hard wear-resisting metal, the coating preferablybeing effected by electro-plating.

Accordingly, it is an object of the invention to produce an article ofmanufacture such as a pump or the like, and various operating partsthereof including intermeshing gears, in an economical manner. Thearticle produced, however, being Wholly efllcient in operation and justas strong and durable as like articles produced by more expensive means.

It is a further object to provide finished teeth upon intermeshing gearsby a new method of production, without expensive tooth cutting ormilling operations.

Still further objects of the invention are to provide as a new articleof manufacture, a machine assembly composed essentially of die castparts; and to produce such an assembly by a '40 method which involves adie casting'of the parts of hard metal or a die casting of themof softermetal followed by the coating of the die castings with a hard andwear-resistant metal; more specifically, to produce a gear or like pumppart or pair of intermeshing gears by such die casting operations.

Other objects and advantages of the invention will be apparent from thefollowing description, when taken in connection with the accompanyingdrawings, wherein there are disclosed certain preferred embodiments ofthe invention.

In the drawings, wherein like reference numerals refer to likepartsthroughout.

Figure 1 is a transverse sectional view through 55 a pump of the geartype showing the operating parts thereof, the view being takensubstantially along the line I-l of Fig. 2.

Figure 2 is a longitudinal sectional view of the pump of Fig. 1 takensubstantially along the line 2--2 thereof. 5

Figure 3 is an exploded view showing the several pump parts and themethod of assembling them, the parts being shown in section similar toFig. 2.

Figure 4 is a view showing the parts of Fig. 3 10 in assembled relation.

Figure 5 is a sectional view of the dies in which the rotor element iscast.

Figure 6 is a perspective view of the cast rotor element. 15

Figure 7 is a sectional view of the dies in which the pinion is cast.

Figure 8 is a perspective view of the cast pinion. Figure 9 is asectional view of the dies in which the crescent member is cast, and 20Figure 10 is a perspective view of the cast crescent member.

For purposes of illustration the invention is shown embodied in a pumpof the type disclosed. However, it is to be understood that the inven-25 tion and the various principles thereof are also applicable to otherdevices, and particularly to devices having intermeshing gear elements,the teeth of which are ordinarily formed by expensive milling and toothcutting operations. 30

The pump shown for purposes of illustration, referring particularly toFigs. 1 to l, inclusive, comprises a casing l0 having an inlet chamber Ii and an outlet chamber l2, and within the body of which rotates thepinion l5 and the rotor I3 35 having an operating shaft 14. A crescentplate l6, secured to the bottom of the pump casing II) by means of studsII, has its crescent shaped projection I8 extending into the pumpinterior and between the rotor and the pinion. The plate 40 also carriesthe pin l6 upon which the pinion I5 is rotatably mounted. An inletconduit 20 communicates with the inlet chamber ll of the casing, and anoutlet conduit 2| communicates with the casing outlet chamber l2. Theconduits 20 4.5 and 2| may be threaded into position within the casing.The drive shaft Id of the rotor is journailed in the pump casing bymeans of a bearing extension 23 formed integral with the casing, withinwhich is threaded the gland 24, which holds the packing 25 in place. Thepacking prevents escape of the fluid being pumped outwardly from thepump interior along the drive shaft of the rotor.

The extending teeth 30 of the rotor bear at their outer sides 3| againstthe interior surface 32 of the casing and at their inner sides 33against the outer surface 34 of the crescent projection. The tops I6 ofthe pinion teeth 31 bear against the inner surface 38 of the crescentand against the interior casing surface at various points in theirrotation, and the bottoms 39 of the pinion teeth cooperate with theinner sides 33 of the rotor teeth: The operation of the pump will bebest understood by reference to Fig. 1. As the rotor is rotatedcounterclockwise, as seen in Fig. 1, by its drive shaft l4, the rotorteeth 30 carry fluid from the inlet conduit 20 and the inlet chamber II,to the outlet chamber l2 and outlet conduit 2|. The rotor in itscounterclockwise movement drives the pinion counterclockwise by reasonof the inter-engagement of the rotor and pinion teeth, and the pinionteeth similarly conduct fluid during their movement from the casinginlet to the casing outlet. The fluid is constrained for movement, asstated, by reason of the engagement of the rotor teeth with the pumpcasing and crescent member, and by reason of the engagement of thepinion teeth with the crescent member. Fluid is prevented from flowingreversely through the pump by reason of the inter-engagement of thepinion and rotor teeth, and by the projecting portion 4| of the casingwhich engages the outer sides of the rotor teeth at this point of toothinter-engagement.

The invention relates primarily to the means by which the several pumpelements are made and to the resulting manner of co-operation of parts.Heretofore it has been the practice to produce the several pump parts bymachine operations. In the case of the gear teeth this requiredexpensive milling and tooth cutting operations. By the present inventionseveral of the parts are die cast. Die casting operations produceaccurate castings, sufficiently accurate so that the parts may beinterengaged without machining operations. Although some metals are notsuitable for die casting because of too high melting point, .excessshrinkage, scale forming tendencies and the like, certain hard metals,particularly certain brass alloys, may be die cast. When such hardmetals are used, no coating of the parts is necessary. If soft diecasting metal is used, such as metal having zinc, lead, tin, or likesoft metal as a base, the die castings are electro-plated or otherwisecoated with a suitable hard metal such as chromium, which thus ren: dersthe casting parts as durable in use as if they were entirely made ofhard metal.

The pump casing I0 is preferably an ordinary casting made in anysuitable way and machined to proper size. Cast iron may be used withsuch fluids to be pumped as would not attack it. In cases where castiron is unsatisfactory, brass or other suitable alloys would be used.

The manner of making the rotor, pinion and crescent member will be bestunderstood by reference first to Figs. 5 to 10, inclusive. The dies forcasting the rotor, as shown in Fig. 5, comprise a top die member 44 anda bottom die member 45 suitably clamped together by clamps 46. Thebottom die member has a hollow portion 41 therein by which the body ofthe rotor is formed, and extending downwardly from the portion 41 arethe wells 48 which form the rotor teeth. The outer portions 49 of thewells are tapered upwardly and outwardly as shown, and the innerportions 50 of the wells are reversely tapered. These tapered portionsgive the wells the necessary draft which permits removal of tooth whichis slightly narrower at its end 5| than at its base portion 52. Suchtaper on the rotor tooth will not interfere with proper meshing with thepinion teeth as will hereinafter appear. The upper die member 44 has acentral opening 53 which serves as a gate for the admission of themetal, and a larger opening 53' for the formation of the rotor endbearing piece l3. The opening 53' is drafted outwardly and downwardlyfor die removal.

The die by which the pinion is cast, as shown in Fig. 7, comprises anupper die member 55 and a lower die member 56, secured together byclamps 51. The lower die member contains the cavity 58 within which thepinion is formed. As shown, the outer portions 59 of the cavity whichform the tops of the teeth and the inner portions 60, which form thebottoms of the teeth, are both tapered upwardly and outwardly to allowthe removal of the casting. Likewise, the tooth forming portions may betapered slightly so that the top portion 6| of the pinion tooth will beformed slightly thicker than the bottom portion 62 of the tooth. Theupper die member has the gate 53 through which the metal is poured.

The dies by which a crescent member is formed are shown in Fig. 9 andcomprise an upper die member 66 and a. lower die member 61, securedtogether by clamps 68. The cavity 69 for forming the crescent memberlies entirely within the lower die member. and the gate 10 is formedthrough the upper die member. The crescent projection forming portion ofthe cavity 69 is tapered upwardly and outwardly at H, thus permittingremoval of the casting. The portion 12 is not tapered. The portions 14are drafted inwardly and downwardly, as shown.

After the rotor and pinion have been cast their outer surfaces areground parallel to remove the casting taper. The rotor and crescentmember are then drilled for the reception of the shafts l4 and I6,respectively, which are press fitted into position. The pinion I5 isalso drilled for the reception of shaft Hi. It is to be noted that thesemachining operations are simple and inexpensive and may be performed.for example, in a grinder and ordinary drilling machine. N0 expensivemachining of the teeth is necessary. After these operations uponthe'parts they are ready for assembly if hard metal has been used in thecasting. If soft metal has been used, the parts must be coated with asuitable hard metal.

The coating is preferably effected by electroplating, and preferablychromium is used, as chromium is hard and a good plating material.However, it is contemplated by the invention that other suitable hardmetals than chromium might be used and that the plating might beeffected by means other than electro-plating, such as by dipping or thelike. Electro-plating is preferred, as an even and secure coating isproduced thereby. The coating may be of such thickness as is required torender the parts strong and durable, but this requires only a thin andrelatively inexpensive plate;

The partsare now ready for assembling, as shown in Figs. 3 and 4. Theshafts I4 and I6 are pressed into position. .The outer sides of therotor teeth, having been ground parallel, may be readily fitted into theinterior 32 of the pump casing.

The pinion may then. be placed in position upon the crescent member andupon the shaft [5, and

these parts thenbrought into engagement with the rotor and assembledinto position by means of bolts ll. A bushing may be fitted into pinionE5 to form the bearing for shaft l6, if desired. The exterior surface ofthe pinion is parallel so that it fits accurately with the parallelinner surface of the crescent projection and with the interior of thecasing. Likewise, the taper on the inner side 33 of the rotor-teethconformsto the taper on the outer surface 34 of. the crescentprojectionand to thetaper at the bottoms 39 of the pinion teeth, so thatthe engagement of the rotor teeth with the crescent projection andpinion teeth will be accurate. Also, the rotor teeth which are narrowedslightly toward their ends 5|, will mesh accurately with the pinionteeth, which are correspondingly widened toward their ends GI whichengage with the end portions ii of the rotor teeth. An accurate toothengagement is thus insured.

By this means of production and assembly an accurate and efficientengagement of parts is secured. The parts are accurately cast by diecasting and are strong and durable.- At the same time expensivemachining operations are avoided.

It is obvious that various changes may be made,

without departing from thespirit of the invention, in the embodimentsused for illustration and in the several method steps disclosed. Itherefore do not wish to be limited to the precise em-- bodiments andmethod steps described and shown, but only as indicated in the followingclaims.

I claim:

1. The method of making a spur gear which comprises casting the gearblank with taperedteeth thereon, and thereafter grinding the peripheralportions of the teeth to an outer cylindrical form, whereby to producethe finished gear.

2. The method of making a gear which comprises die-casting a spur gearblank with axially extending gear teeth formed thereon, the root portionof the gear being of truncated conical form, said gear teeth tapering inthickness in the direction of taper of said conical root portion and 7having their peripheral surfaces tapering in said direction, andmachining the peripheral surfaces rfmly of the gear to a substantiallycylindrical orm.

3. The method of forming and interfltting gears which comprisesdie-casting a gear with teeth having their root portions inclinedlongitudinally toward the gear axis and of uniformly decreasingthickness in the same direction, die-casting a sec- 0nd gear with teethhaving root portions of similar inclination and of similarly decreasingthickness, and interfitting the gears with the root portions of theteeth of the respective gears inclined oppositely and the thicker toothportions on one of the gears in mesh with the thinner tooth portions onthe other gear.

4. The method of making a machine unit which comprises die-casting arotor member having axially extending internal gear teeth, having allgear surfaces thereof tapered toward one end, the exterior portions'ofthe rotor being tapered in "the same direction, machining the exteriorsurcomprises die-casting a rotor member having axially extendinginternal gear teeth having all gear surfaces thereof tapered toward oneend, the exterior portions of the rotor being tapered in the samedirection, machining the exterior surface of the rotor to provide aportion of substantially cylindrical form defined by spaced apart outertooth surfaces, die-casting a spur gear with axially extending externalgear teeth, having all gear surfaces thereof tapered in an axialdirection, machining the spur gear to an outer cylindrical form, meshingsaid gears in geared relationship with the tapered surfaces extendingoppositely and with the cylindrical surfaces of the two gears insubstantial tangency.

BERT A.

